The present invention relates to sweeper units and, in particular, broom elements and their mounting means used on railway ballast regulators. Ballast regulators are employed to perform such functions as plowing and sweeping the gravel (or "ballast") surrounding and supporting railway tracks and ties.
Existing sweeper units employing solid broom elements use broom reels with the broom elements aligned parallel to the axis of the broom reel. The effect of this arrangement is to create a considerable vibration caused by the striking (or "thumping") against the ballast at one time of all the broom elements in a given row.
The broom elements presently utilized take one of three basic forms: solid cylindrical rods, solid squared isosceles trapezoid or solid horseshoe shape rods and a hollow tube or plugged hollow tubes. All of these elements have been constructed of various compounds and combinations of materials in an effort of improving element life and sweeping action. Traditionally, the hollow tube form has been the most popular due to the ability to substitute readily available used train brake hoses for the hollow tubes. However, the solid form of broom elements are more durable and perform superior sweeping function over the ballast surface.
In the case of the first two types of elements, attachment to the broom reel in machines in use today has involved the use of clamping holders which rigidly retain the broom elements in place through friction by compressing the broom elements. Such an arrangement is shown, for example, in U.S. Pat. No. 4,484,373. These clamping holders require considerable pressure to retain the broom elements in place; as such, replacement of broom elements is a burdensome procedure requiring compression of broom elements and manipulation of bolting and fastening means on the clamping holders. Replacement of broom elements is further handicapped by the tendency of the clamping means to become fixed due to the considerable pressure involved and the exposure of the holders to adverse environmental conditions. Additionally, the construction of the holders for these elements has been such that the one side of the holder receiving the side of the broom elements upon impact is contoured but the other side of the holder (i.e. the side which receives the rebounding broom element) is a straight, non-contoured edge. The result is that these holders tend to prematurely damage broom elements by unduly stressing the broom elements at the impact point between the broom element and the holder upon rebound.
Tightly clamped broom elements also present another problem of high stress in the broom element at the point where the clamp holding the broom element terminates. The repeated flexure of the broom element at the clamping point actually heats the broom element and very often the broom element will fail at that point before the end of the broom element has worn to the point of requiring replacement.
Attachment of hollow tubes has been accomplished by inserting the tube over a stepped nipple element. Although stepped nipple elements can be readily arranged to avoid the aforementioned "thumping" problem, this form of broom element has other severe limitations. By the very nature of stepped nippled elements, considerable manipulation and pressure must be asserted to the hollow tubes in order to install and replace them. Moreover, hollow tubes have a shorter life and are not as durable as solid broom elements.
A problem present with all of the aforementioned designs is that the broom elements located over the tracks, which are some 7 inchs higher than the rest of the surface being swept, tend to receive extreme punishment and deteriorate much faster than the other broom elements. Although hollow tube broom elements used with stepped nipple holders tend to be more forgiving under the stresses caused by the closer sweeping surface of the rails, the combination of the hollow tubes and the stepped nipple elements do not sweep as well or last as long as is desired with respect to the sweeping of the ballast surface.